单项选择题

In some countries, societal and familial treatment of the elderly usually reflects a great degree of independence and individualism. Their financial support is often provided by social security or welfare systems which decrease dependence on their family. Additionally, older people may seek their own friends rather than become too emotionally dependent on their children. Senior citizens centers provide a means for peer-group association within one’s own age groups. There are problems, however, with growing old, in the United States. Glorification of youth and indifference to the aged have left many older people alienated and alone.
Some families send their older relatives to nursing homes rather than integrate them into the homes of the children or grandchildren. This separation of the elderly from the young has contributed to the isolation of an increasingly large segment of society. On the other hand, there are many older people who choose to live in retirement communities where they have the companionship of other older people and convenience of many recreational and social activities close home.
The treatment of the elderly can be further understood by distinguishing between nuclear and extended family structures. In the United States the nuclear family, which consists of the father, the mother, and the children, is considered "the family". The extended family, common in other cultures, includes grandparents, aunts, uncles, cousins, nephews, nieces, and children in law. The distinction between the nuclear and extended family is important because it suggests the extent of family ties and obligations. In extended families the children and parents have strong ties and obligations to relatives. It is common in these families to support older family members, to have intensive contact with relatives, and to establish communal housing.
The American nuclear family usually has its own separate residence and is economically independent of other family members. Relatives are still considered "family" but are often outside the basic obligations that people have to their immediate families. When couples many, they are expected to live independently of their parents and become "heads of households" when they have children. It is not unusual in times of financial need for nuclear family members to borrow money from a bank rather than from relatives. Grandparents, aunts, uncles, and cousins, then, are not directly involved in the same way as they would be in an extended family structure.
The word "peer-group" (Line 4, Para. 1 ) most probably means a group in which